The present invention generally relates to implantable medical devices, such as of the types for monitoring physiological parameters. More particularly, the invention relates to anchors for medical implants, methods of manufacturing anchors, and methods of placing medical implants, wherein the anchors and methods are suitable for use in procedures performed to diagnose, monitor, and/or treat cardiovascular diseases, including procedures performed to monitor pressure in the left side of the heart.
Congestive heart failure (CHF), a condition in which the heart fails to pump efficiently, currently affects about 4.8 million patients (over 400,000 new patients per year in the U.S.), accounts for about 5 to 10% of all hospitalizations, and costs over $38 billion in the U.S. Following diagnosis of congestive heart failure, physicians typically monitor disease progression on a continuing basis to better tailor treatment. The best course of action for a tailored treatment involves monitoring of the pressures of the left side of the heart, particularly left ventricular end-diastolic pressure (LVEDP, also known as left ventricular filling pressure) and mean left-atrium pressure (MLAP). These pressures are recognized as the best parameters for characterizing congestive heart failure in patients. Clinical evaluation of LVEDP or MLAP is generally performed using a cardiac catheterization procedure, which provides a snapshot of pressure data a few times per year at most, carries morbidity, and is expensive. More recently, miniaturized medical implants have been developed that are adapted to be delivered with a catheter and implanted into a wall of the heart, such as the atrial septum. Once implanted, the implant is able to chronically monitor physiological parameters of the heart, for example, hemodynamic monitoring of left atrial biopressure waveforms such as LVEDP or MLAP. As such, implants of this type are well suited for diagnosing, monitoring, and/or treating cardiovascular diseases such as congestive heart failure, as well as congenital heart disease (CHD).
Monitoring pressures within the heart, and particularly pressures of the left side of the heart, is a very challenging task for many reasons, most importantly the potentially fatal outcome of any thrombi caused by the implant. Bleeding, thromboembolism and arrythmias are potentially fatal complications. Because smaller implant sizes are capable of reducing the risk for these complications, miniaturized MEMS (microelectromechanical systems) are desirable for chronic implantation. Notable examples of MEMS implants are disclosed in U.S. Pat. Nos. 6,140,144, 6,926,670, 6,968,743, 7,211,048, 7,615,010 and 7,686,762 and U.S. Published Patent Application Nos. 2006/0047205, 2007/0032734, 2008/0077016, 2008/0269573, 2009/0005656, 2009/0105557, 2009/0105784 and 2009/0143696. Pressure monitoring systems of the type disclosed in these patent references may comprise two primary components: the implant comprising an implantable telemetric pressure sensor that is batteryless or makes use of a small battery, and a companion hand-held reader. The implant further includes custom electronics for processing the output of the sensor and an antenna for telemetry and, if necessary or desired, for tele-powering the sensor. Telemetry and tele-powering can be achieved via various techniques, including but not limited to magnetic telemetry (including RF), acoustic waves, ultrasonic waves, with the currently preferred technique typically being magnetic telemetry. The reader transmits power to the sensor, and the sensed pressure is in turn transmitted back to the reader. Data collected from the sensor can then be used by a physician to tailor the treatment of the patient. Miniaturized implants of this type can provide chronic, continuous bio-pressure measurements and support the trend toward home health monitoring. In some cases, the implant may also be configured or adapted to perform additional functions, such as monitoring temperature or delivering a drug or electric signal to the muscles/nerves.
Monitoring pressures with a miniaturized implant chronically implanted within the heart is also complicated by the challenges of devising a reliable anchoring system that does not increase the risk of thrombi. Notable examples of anchors suitable for this purpose are disclosed in U.S. Pat. Nos. 7,317,951 and 7,634,319 and U.S. Published Patent Application No. 2007/0179583. Though significant advances have been achieved with these anchoring systems, further improvements are desired.